wow, big question! Not an easy one to answer without some level of details...
If you were in North America or Europe I would say don't waste your time and money, you are 3-5 years too late. But since you are in a developing/3rd world country, then there might not be much existing competition either from the original manufacturers or from other re-branded solutions.
The problem you will have is generating profit from products whose prices have not stopped decreasing for the last 5 years. At the moment, if you can make $50 on a 2MP varifocal outdoor dome with IR, you are lucky (and you had better hope the quality is good because a couple of bad cameras per hundred and your profit dwindles)
Since 2009, we have done what you describe twice and I'll try to help define the process the first time we did it (when we were new at this): We first used ACTi cameras. The relationship was excellent with ACTi, they were (and still are) a minor player "not from China" and the initial camera quality and image quality was above average for 2010.
The process of starting a new OEM brand is extremely time-consuming (not necessarily complex but each step, if done well, takes a lot of time). It took us close to 2 years to fully expand our camera offering using ACTi (about 30 camera models total).
These are the steps involved in qualifying an OEM manufacturer and putting out an OEM product: identifying the partner you want to deal with; approach with the partner and negotiation with the partner; identify the camera models you want to test and qualify (this can be anything from 3 to 50+ cameras depending on your business plan and target market. This is the longest and most difficult part and the one where you MUST spend the most time. You need to test, qualify and understand every single model of camera you OEM and there needs to be a market driven reason for introducing each and every model or you will lose your shirt in dead inventory).
Once the camera (and mounts and accessories) models are chosen and tested you also need to do the same process to qualify the recorders you will want (very important and as time-consuming as the cameras). You will need to source additional things like hard drives, perhaps power supplies, maybe wiring and other items.
Once the cameras and recorder models are chosen and tested (you are now more than 6-9 months into the process, maybe more if you have done the technical testing work correctly), you need to start on the marketing work of being an OEM 9you might have already started on this if you are convinced of the market viability): find a brand name (sounds silly but it took us more than 3 months back-and-forth with brand lawyers to be sure we were not using someone else's brand), customization of the software user interface (complex, expensive and time-consuming); customization of the firmware user interface (and functionality); logo design, box design and contents; writing the manuals (or at least personalizing them; they can be hundreds of pages long!); translating everything from English into your local language; doing the website design; social media; planning industry security event participation; hiring and training tech support (an ongoing process); hiring and training sales staff (an ongoing process); having someone to answer the phone when they are not happy (an ongoing process)... and so on and so on ans so on... By the end of all of this, you are more than 1 year into the whole thing (probably closer to 2 years) when you start selling and generating revenue.
We had 2 long-term issues with ACTi that will be common no matter which OEM manufacturer you choose: the long-term quality needs to be high or you will simply not sell anything repetitively to customers (this was poor with ACTi and did not show up in any of our extensive tests before release- in some instances - with anything autofocus, for example- we had over 25% failure rate of a line of cameras after 1 year); secondly, we could not pretend to be Axis or Avigilon and demand 50% more for our cameras- our name was new to the market and we needed to compete on a daily basis- so our margins gradually diminished as the Chinese products (especially HIK) gained popularity. We needed to compete against these Chinese products or die out. ACTi was never able to provide us with OEM pricing to even remotely approach where we needed to be against HIK.
So after 4 years of reasonably successful OEM of ACTi (and 1 year of dramatically losing our customers as HIK came in the market), we had to make a decision: find a new OEM partner that could give us long term quality AND the ability to compete OR get out of the camera market.
We chose to find a new partner and are now in the 3rd year of that new partnership. We sell 5x more cameras in volume (compared to 2014) but we make essentially the same profit at the end of the year because of the tiny profit per camera.
In your original question you asked for advice. This is my 2 cents worth:
1. If HIK/Dahua/Hanwha are present in your local marketplace, then do NOT chose them as an OEM partner. You will not be able to differentiate yourself from them and will simply fight over price all the time. And if they are not in your local market, as soon as you have some success they will screw you and enter your market.
2. If you are not technical, surround yourself with competent technical people to advise you (from the security industry) on product selection.
3. This is a major endeavor you are considering. it will take time if you do it- do not cut corners or skip steps or you will regret it later.
4. If HIK/Dahua/Hanwha are present in your local marketplace, then you should seriously consider not doing this at all unless you are convinced that you have something more of value to provide the industry. There are already enough good-quality low-cost cameras on the market. if you do this, you need to provide more to the market (such as better stock levels, better tech support, local language support, local sales resources, etc...) All of these things are of value to the marketplace and they are essentially the only reason why an OEM can eventually succeed.
5. If you are simply providing an existing camera under a different brand name (with no additional services), you will fail. The gold rush for OEMs was 5 years ago and you are late to the game.
Sorry this answer was so long (I could have doubled this with a description of our current camera OEM relationship) and I hope that this little bit can help in your process.
BTW: we considered all of these risks and opportunities in 2009 in our business plan. The one thing we did not consider was that HIK would release good quality IP cameras at $200 (now less than $100) when everyone else was at $300-$500.
“The best laid schemes o' mice an' men / Gang aft a-gley.” (Robert Burns)